cciss: initialize struct scsi_req

The changes in "block: Make most scsi_req_init() calls implicit" mean
that every driver that supports the generic scsi ioctls needs to
call scsi_req_init on newly allocated requests, but that commit didn't
add the call to the ccіss driver.  Fix that to avoid crashes when
udev issues SG_IO commands.

Fixes: ca18d6f7 ("block: Make most scsi_req_init() calls implicit")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Jens Axboe <axboe@kernel.dk>